Ammonium Electrode
Instruction Manual
2
GENERAL PREPARATION
Electrode Preparation
Remove any rubber cap(s) covering the electrode tip(s) and the rubber inserts covering the filling
holes of the reference electrode. Fill the combination electrode or the reference electrode with the
filling solution shipped with the electrode to a level just below the fill hole. No preparation is
required for a sealed reference electrode. Gently shake the electrode downward in the same manner
as a clinical thermometer to remove any air bubbles that might be trapped behind the ammonium
membrane. Prior to first usage, or after long term storage, immerse the ammonium electrode in
ammonium standard for thirty minutes. The electrode is now ready for use. Connect the electrode(s)
to the proper terminal(s) as recommended by the meter manufacturer.
Electrode Slope Check (with standard pH/mV meter)
(Check electrodes each day)
To a 150 ml beaker, add 100 ml of distilled water and 2 ml of ISA. Place the beaker on a magnetic
stirrer and begin stirring at a constant rate. After assuring that the meter is in the mV mode, lower
the electrode tip(s) into the solution.
Using a pipet, add 1 ml of 0.1M or 1,000 ppm ammonium standard to the beaker. When the reading
is stable, record the millivolt reading. Using a pipet, add 10 ml of the standard used above to the
beaker. When the reading has stabilized, record the millivolt reading.
Determine the difference between the two readings. A difference of 56
±
2 mV indicates correct
electrode operation, assuming the solution temperature is between 20o and 25oC. See the
TROUBLESHOOTING
section if the potential change is not within this range.
Slope is defined as the change in potential observed when the concentration changes by a factor of
10.
Electrode Slope Check (with ion meter)
(Check electrodes each day)
Prepare standard ammonium solutions whose concentrations vary by tenfold. Use either the 0.1M
NH
4
+1
or the 1,000 ppm NH
4
+1
standard stock solutions. Use the serial dilution method for this
preparation.
To a 150 ml beaker, add 100 ml of the lower value standard and 2 ml of ISA. Place the beaker on
the magnetic stirrer and begin stirring at a constant rate. Lower the electrode tip(s) into the solution.
Assure that the meter is in the concentration mode. Adjust the meter to the concentration of the
standard and fix the value in the memory according to the meter manufacturer's instructions.
Rinse the electrode(s) with distilled water and blot dry. To a 150 ml beaker, add 100 ml of the
higher value standard and 2 ml of ISA. Place the beaker on the magnetic stirrer and begin stirring at
a constant rate. Lower the electrode tip(s) into the solution.
Adjust the meter to the concentration of the standard and fix the value in the memory. Read the
electrode slope according to the meter manufacturer's instructions. Correct electrode operation is
